Constant temperature and calorimetric sensors are types of which flow sensors?

• A. Mass
• B. Velocity
• C. Volume
• D. Differential

Answer: (A)

Thermal mass-flow sensing is what's being tested here. Constant-temperature and calorimetric sensors determine how much gas mass passes per second by how heat is carried away by the flow. In a constant-temperature sensor, the element is kept at a fixed temperature; as gas flows past, it removes heat, so the electronics inject more power to hold the temperature steady. The amount of power required is proportional to the mass flow rate, giving a direct measure of mass flow. In a calorimetric sensor, the heat transfer from the heated element to the flowing gas is measured—again, the rate of heat removal relates to how much mass is moving per second. This approach contrasts with velocity sensors, which infer flow speed, volume sensors, which track how much volume moves per unit time, or differential sensors that rely on pressure differences.